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A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Surface Characterization, Deposition and Modification".

Deadline for manuscript submissions: closed (30 June 2021) | Viewed by 17165

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Prof. Dr. Yung-I Chen

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Department of Optoelectronics and Materials Technology, National Taiwan Ocean University, Keelung, Taiwan
Interests: bond coats; diffusion barriers; glass molding technology; high-entropy alloy films; internal oxidation; metallic coatings; nanocomposite nitride films; thin-film metallic glasses; transition metal nitride films
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Dear Colleagues,

Multilayer coatings consist of sublayers with alternative variation in chemical concentrations or crystalline structures. The multilayer-structure is beneficial for improving oxidation resistance, enhancing mechanical properties, reducing internal stress, inhibiting crack propagation, and improving fracture toughness. For example, a columnar crystalline structure formed in a monolithic coating is interrupted due to the distinct characteristics between the sublayers. With the introduced interfaces, multilayer hard coatings have displayed hardness enhancements due to dislocation blocking between interfaces, lattice mismatch, and Hall–Petch effects. Multilayer coatings comprise various assemblies, such as metal/metal, metal/nitride, nitride/nitride, and oxide/metal. This Special Issue on "Multilayer and Functional Graded Coatings" is open to all original research and critical review articles in the relevant topics.

Prof. Yung-I Chen
Guest Editor

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Keywords

Corrosion protection
Diffusion barriers
Gradient concentration
Laminated coatings
Mechanical properties
Multilayer coating
Optical coating
Oxidation resistance
Protective coatings

Published Papers (6 papers)

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Research

13 pages, 10540 KiB

Open AccessArticle

Structural, Optical, and Electrical Properties of Copper Oxide Films Grown by the SILAR Method with Post-Annealing

by Wen-Jen Lee and Xin-Jin Wang

Coatings 2021, 11(7), 864; https://doi.org/10.3390/coatings11070864 - 19 Jul 2021

Cited by 30 | Viewed by 3712

Abstract

Copper oxides are widely used in photocatalysts, sensors, batteries, optoelectronic, and electronic devices. In order to obtain different material properties to meet the requirements of different application fields, varied technologies and process conditions are used to prepare copper oxides. In this work, copper oxide films were grown on glass substrates by a successive ionic layer adsorption and reaction (SILAR) method with subsequent annealing under an atmospheric environment. The films were characterized by using an X-ray diffractometer, Raman spectrometer, Scanning electron microscope, UV-Visible-NIR spectrophotometer, and Hall Effect measurement. The results show that the as-deposited film has a Cu₂O crystal structure, which begins to transform into Cu₂O-CuO mixed crystal and CuO crystal structure after annealing at 300 °C for a period of time, resulting in the bandgap of being reduced from 1.90 to 1.34 eV. The results show that not only are the crystal structure and bandgap of the films affected by the post-annealing temperature and time, but also the resistivity, carrier concentration, and mobility of the films are varied with the annealing conditions. In addition, the film with a Cu₂O-CuO mixed crystal shows a high carrier mobility of 93.7 cm²·V⁻¹·s⁻¹ and a low carrier concentration of 1.8 × 10¹² cm⁻³ due to the formation of a Cu₂O-CuO heterojuction. Full article

(This article belongs to the Special Issue Multilayer and Functional Graded Coatings)

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13 pages, 5532 KiB

Open AccessArticle

Curved-Mechanical Characteristic Measurements of Transparent Conductive Film-Coated Polymer Substrates Using Common-Path Optical Interferometry

by Bor-Jiunn Wen and Jui-Jen Hsu

Coatings 2021, 11(7), 766; https://doi.org/10.3390/coatings11070766 - 25 Jun 2021

Cited by 1 | Viewed by 1478

Abstract

This study proposes a method for measuring curved-mechanical characteristics based on a whole-folding test for transparent conductive film-coated polymer substrates using common-path optical interferometry. Accordingly, 80-, 160-, and 230-nm indium tin oxide films coated on 40 × 40 mm 125-μm-thick polyethylene terephthalate (PET) substrates, and monolayer graphene films coated on 40 × 40 mm 250-μm-thick PET substrates are inspected and analyzed under the curving conditions of 50-, 30-, 20-, and 10-mm radii before and after an 11,000 whole-folding cycle test based on a 10-mm folding radius. This study utilizes the changes in the phase retardations of transparent conductive film-coated polymer substrates under different curving conditions before and after 11,000 whole-folding cycles to analyze the substrates’ residual stress characteristics that were the direct result of manufacturing process parameters. The results from this study of curved-mechanical characteristic measurements of flexible transparent conductive substrates can provide designers with improved product development and can assist manufacturers in improving the manufacturing design of enhanced coating processes. Full article

(This article belongs to the Special Issue Multilayer and Functional Graded Coatings)

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14 pages, 6683 KiB

Open AccessArticle

Mechanical Properties and Diffusion Barrier Performance of CrWN Coatings Fabricated through Hybrid HiPIMS/RFMS

by Li-Chun Chang, Cheng-En Wu and Tzu-Yu Ou

Coatings 2021, 11(6), 690; https://doi.org/10.3390/coatings11060690 - 09 Jun 2021

Cited by 4 | Viewed by 2268

Abstract

CrWN coatings were fabricated through a hybrid high-power impulse magnetron sputtering/radio-frequency magnetron sputtering technique. The phase structures, mechanical properties, and tribological characteristics of CrWN coatings prepared with various nitrogen flow ratios (f_N2s) were investigated. The results indicated that the CrWN coatings prepared at f_N2 levels of 0.1 and 0.2 exhibited a Cr₂N phase, whereas the coatings prepared at f_N2 levels of 0.3 and 0.4 exhibited a CrN phase. These CrWN coatings exhibited hardness values of 16.7–20.2 GPa and Young’s modulus levels of 268–296 GPa, which indicated higher mechanical properties than those of coatings with similar residual stresses prepared through conventional direct current magnetron sputtering. Face-centered cubic (fcc) Cr₅₁W₂N₄₇ coatings with a residual stress of −0.53 GPa exhibited the highest wear and scratch resistance. Furthermore, the diffusion barrier performance of fcc CrWN films on Cu metallization was explored, and they exhibited excellent barrier characteristics up to 650 °C. Full article

(This article belongs to the Special Issue Multilayer and Functional Graded Coatings)

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15 pages, 8877 KiB

Open AccessArticle

A Fully Inkjet-Printed Strain Sensor Based on Carbon Nanotubes

by Hsuan-Ling Kao, Cheng-Lin Cho, Li-Chun Chang, Chun-Bing Chen, Wen-Hung Chung and Yun-Chen Tsai

Coatings 2020, 10(8), 792; https://doi.org/10.3390/coatings10080792 - 14 Aug 2020

Cited by 24 | Viewed by 3893

Abstract

A fully inkjet-printed strain sensor based on carbon nanotubes (CNTs) was fabricated in this study for microstrain and microcrack detection. Carbon nanotubes and silver films were used as the sensing layer and conductive layer, respectively. Inkjet-printed CNTs easily undergo agglomeration due to van der Waals forces between CNTs, resulting in uneven films. The uniformity of CNT film affects the electrical and mechanical properties. Multi-pass printing and pattern rotation provided precise quantities of sensing materials, enabling the realization of uniform CNT films and stable resistance. Three strain sensors printed eight-layer CNT film by unidirectional printing, rotated by 180° and 90° were compared. The low density on one side of eight-layer CNT film by unidirectional printing results in more disconnection and poor connectivity with the silver film, thereby, significantly increasing the resistance. For 180° rotation eight-layer strain sensors, lower sensitivity and smaller measured range were found because strain was applied to the uneven CNT film resulting in non-uniform strain distribution. Lower resistance and better strain sensitivity was obtained for eight-layer strain sensor with 90° rotation because of uniform film. Given the uniform surface morphology and saturated sheet resistance of the 20-layer CNT film, the strain performance of the 20-layer CNT strain sensor was also examined. Excluding the permanent destruction of the first strain, 0.76% and 1.05% responses were obtained for the 8- and 20-layer strain sensors under strain between 0% and 3128 µε, respectively, which demonstrates the high reproducibility and recoverability of the sensor. The gauge factor (GF) of 20-layer strain sensor was found to be 2.77 under strain from 71 to 3128 µε, which is higher than eight-layer strain sensor (GF = 1.93) due to the uniform surface morphology and stable resistance. The strain sensors exhibited a highly linear and reversible behavior under strain of 71 to 3128 µε, so that the microstrain level could be clearly distinguished. The technology of the fully inkjet-printed CNT-based microstrain sensor provides high reproducibility, stability, and rapid hardness detection. Full article

(This article belongs to the Special Issue Multilayer and Functional Graded Coatings)

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9 pages, 3016 KiB

Open AccessArticle

Thermal Stability, Hardness, and Corrosion Behavior of the Nickel–Ruthenium–Phosphorus Sputtering Coatings

by Yu-Cheng Hsiao and Fan-Bean Wu

Coatings 2020, 10(8), 786; https://doi.org/10.3390/coatings10080786 - 13 Aug 2020

Cited by 1 | Viewed by 2108

Abstract

Nickel–ruthenium–phosphorus, Ni–Ru–P, alloy coatings were fabricated by magnetron dual-gun co-sputtering from Ni–P alloy and Ru source targets. The composition variation and related microstructure evolution of the coatings were manipulated by the input power modulation. The as-prepared Ni–Ru–P alloy coatings with a Ru content less than 12.2 at.% are amorphous/nanocrystalline, while that with a high Ru content of 52.7 at.% shows a feature of crystallized Ni, Ru, and Ru₂P mixed phases in the as-deposited state. The crystallized phases for high Ru content Ni–Ru–P coatings are stable against annealing process up to 600 °C. By contrast, the amorphous/nanocrystalline Ni–Ru–P thin films withstand a heat-treated temperature up to 475 °C and then transform into Ni(Ru) and Ni_xP_y crystallized phases at an annealing temperature over 500 °C. The surface hardness of the Ni–Ru–P films ranges from 7.2 to 12.1 GPa and increases with the Ru content and the annealing temperatures. A highest surface hardness is found for the 550 °C annealed Ni–Ru–P with a high Ru content of 52.7 at.%. The E_corr values of the heat-treated amorphous/nanocrystalline Ni–Ru–P coatings become more negative, while with a high Ru content over 27.3 at.% the Ni–Ru–P films show more negative E_corr values after annealing process. The pitting corrosion feature is observed for the amorphous/nanocrystalline Ni–Ru–P coatings when tested in a 3.5M NaCl solution. Severer pitting corrosion is found for the 550 °C annealed Ni–Ru–P coatings. The development of Ni(Ru) and Ni_xP_y crystallized phases during annealing is responsible for the degeneration of corrosion resistance. Full article

(This article belongs to the Special Issue Multilayer and Functional Graded Coatings)

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12 pages, 4568 KiB

Open AccessArticle

Effects of Substrate Rotation Speed on Structure and Adhesion Properties of CrN/CrAlSiN Multilayer Coatings Prepared Using High-Power Impulse Magnetron Sputtering

by Jian-Fu Tang, Chun-Hong Huang, Ching-Yen Lin, Fu-Chi Yang and Chi-Lung Chang

Coatings 2020, 10(8), 742; https://doi.org/10.3390/coatings10080742 - 29 Jul 2020

Cited by 12 | Viewed by 2993

Abstract

We investigated the effects of substrate rotation speed on the structural and mechanical properties of CrN/CrAlSiN multilayer coatings produced using high-power impulse magnetron sputtering (HiPIMS) on silicon and high-speed steel (HSS) substrates. Structural analysis and characterization of the multilayer coatings were performed using an X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), an electron probe microanalyzer (EPMA), and a transmission electron microscope (TEM). The thickness of the bi-layer film depended on the substrate rotation speed, as follows: 12 (1.5 rpm), 9.5 (2 rpm), 6 (3 rpm), 4 (4 rpm), and 3.2 nm (5 rpm). The results revealed that the hardness and coating–substrate adhesion strength increased inversely with the thickness of the bi-layer. TEM analysis revealed smaller columnar structures in thinner CrN/CrAlSiN multilayer coatings. The highest results for hardness (20.1 GPa), elastic modulus (336 GPa), and adhesion strength (77 N) were obtained at a substrate rotation speed of 5 rpm. We also investigated the adhesion properties of the multilayer structures and formulated a hypothesis to explain adhesion strength. Full article

(This article belongs to the Special Issue Multilayer and Functional Graded Coatings)

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